//合并两个有序链表
//测试链接：https://leetcode.cn/problems/merge-two-sorted-lists/
public class MergeTwoLists {

    public class ListNode {
        int val;
        ListNode next;
        ListNode() {}
        ListNode(int val) { this.val = val; }
        ListNode(int val, ListNode next) { this.val = val; this.next = next; }

    }
    public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
        if(list1 == null) return list2;
        if(list2 == null) return list1;
        ListNode head = null;
        if(list1.val < list2.val) {
            list1.next = mergeTwoLists(list1.next,list2);
            head = list1;
        }
        else {
            list2.next = mergeTwoLists(list1,list2.next);
            head = list2;
        }
        return head;

    }
}
